At some point in the not distant future, some reporter - probably a not altogether pleasant one - will ask Trump: "How does it feel to be losing so badly? Just on a personal level? Does it hurt? Do regret getting into this?" It won't be pretty because Trump's ego is fragile. From there I suspect you'll see it cropping up in campaign attacks from every direction.
And as Marshall points out, he's not only losing, he's got two women making scathing attacks on his ego.
For all the ups and downs, look at this chart to see the basic stability of the presidential race.